There is no single genetic mechanism behind sex differences in different species and the existence of two sexes seems to have evolved multiple times independently in different evolutionary lineages. Patterns of sexual reproduction include

isogamous species with two or more mating types with gametes of identical form and behavior (but different at the molecular level),

oogamous species, which include humans in which the female gamete is very much larger than the male and has no ability to move. Oogamy is a form of anisogamy. There is an argument that this pattern was driven by the physical constraints on the mechanisms by which two gametes get together as required for sexual reproduction.

Plant reproductive morphology

Plant reproductive morphology is concerned with the physical form and structure (the morphology) of those parts of plants directly or indirectly concerned with sexual reproduction.

Among all living organisms, flowers, which are the reproductive structures of angiosperms, are the most varied physically and show a correspondingly great diversity in methods of reproduction. Plants that are not flowering plants (green algae, mosses, liverworts, hornworts, ferns and gymnosperms such as conifers) also have complex interplays between morphological adaptation and environmental factors in their sexual reproduction. The breeding system, or how the sperm from one plant fertilizes the ovum of another, depends on the reproductive morphology, and is the single most important determinant of the genetic structure of nonclonal plant populations. Christian Konrad Sprengel (1793) studied the reproduction of flowering plants and for the first time it was understood that the pollination process involved both biotic and abiotic interactions. Charles Darwin's theories of natural selection utilized this work to build his theory of evolution, which includes analysis of the coevolution of flowers and their insectpollinators.

Female (1933 film)

Plot

Alison Drake (Ruth Chatterton) is the wealthy owner and hard-driving, no-nonsense head of a large automobile company, inherited from her father. Her work has caused her to lose her youthful romanticism, and she has casual affairs with men, including her own employees.

Alison hosts a party at her mansion, but becomes fed up with the men out to either sell her things or marry her for her money. She dresses down and goes to an amusement park, where she picks up a man at a shooting gallery. They have fun together, but he refuses her offer to go home with him.

The next day, they meet again at her factory. To their mutual astonishment, he turns out to be Jim Thorne (George Brent), a gifted engineer she has ordered her underlings to hire away from her competition. Saying that she has no time now, Alison has him come to her mansion that night, supposedly to discuss his plans for the company in detail. She attempts to seduce him, but he rejects her as anything other than his employer.